(1) Field of the Invention
The present invention relates to accelerometers and particularly fibre optic accelerometers for use in interferometers.
(2) Description of the Art
The need to monitor extremely low levels of vibration in areas such as security, seismic survey and condition monitoring of machinery and such like has spurred the development of ever more sensitive accelerometers. Fibre optic technology has been applied to this particular field in the form of fibre-optic accelerometers based on interferometric techniques. The compliant cylinder approach to the design of a fibre-optic accelerometer is particularly effective when incorporated in such an interferometer. In one known approach a seismic mass is held in place by two compliant cylinders and around the circumference of each cylinder there being wound a single mode optical fibre, which form the arms of an interferometer. In another approach, a single compliant cylinder 2 loaded with a seismic mass 4 as shown in FIG. 1 is wound circumferentially with an optical fibre 6.
Whilst the abovementioned approaches have found acceptance, there remains a need to increase yet further the sensitivity of the accelerometer beyond that currently achievable and in particular to do so without any increase in component size. The present invention seeks to improve the sensitivity of a fibre wound compliant cylinder accelerometer whilst simultaneously seeking to avoid additional cost and complexity of construction.